Method and system for accessing multimedia data over public switched telephone network

ABSTRACT

A public switched telephone network for providing information from a multimedia information server to any one of a plurality of subscriber premises, comprises a central office receiving multimedia information signals from a multimedia information server and orders from a prescribed subscriber. The central office includes a gateway system for conveying routing data in response to subscriber orders and a switch for routing multimedia signals from the server to the prescribed subscriber in accordance with the routing data. An interface at the central office transmits and receives audio telephone service signals, subscriber control signals and digital multimedia information signals on first, second and third signal channels. Each subscriber premises includes an interface for transmitting and receiving audio telephone service signals, subscriber control signals and digital multimedia information signals on the three signal channels. A plurality of subscriber local loops interconnect each subscriber interface and the central office interface. Multimedia information is collected from information providers and stored at media servers that provide a library of data and control sessions. Software modules at the media servers and resident terminals enable interactive multimedia session building, sharing of databases and joint authoring of multimedia presentations.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of application Ser. No.08/455,782 filed May 31, 1995 now U.S. Pat. No. 5,625,406 and adivisional application of U.S. patent application Ser. No. 08/099,381filed on Jul. 30, 1993, now U.S. Pat. No. 5,528,281 which is acontinuation-in-part application of application Ser. No. 08/042,107filed on Apr. 1, 1993 now abandoned, which in turn is acontinuation-in-part of copending application Ser. No. 07/766,535 filedSep. 27, 1991 now U.S. Pat. No. 5,247,347, all assigned to the assigneeof the present invention.

TECHNICAL FIELD

The invention relates to data distribution using the Public SwitchedTelephone Network (PSTN), and, more particularly, to distribution ofmultimedia data to subscribers over a PSTN.

BACKGROUND ART

Advances in personal computer capabilities have created increaseddemands on data base sources to supply information to households andbusiness. Corresponding increases in data availability, storage,retrieval and transmission capabilities have supported multimiedia datapresentation of information. Multimedia presentations include, inaddition to conventional text, still-images, animation, slow and fastscan video, and graphics format visual presentations. Multimedia alsoincludes sound data presented together with, or independent of, one ormore visual presentations. A multimedia presentation can range from theequivalent of an electronic book including plain text in combinationwith still images to full motion video presentations of feature movies.Thus, multimedia spans a wide spectrum of data storage, retrieval andtransmission requirements to present information in various formats tosystem subscribers.

Considerable potential exists to improve the availability of multimediaservice to the public. One example is in education. Several segments ofsociety find themselves remote from learning resources. Educators havetraditionally tried to find a way to overcome the limitations imposed byphysical distance, on one hand by using school buses to transport peopleand on the other by employing telecommunications to transportinformation. However, physical distance remains a barrier to educationdespite numerous experiments and studies to solve the problem. Knownproposals to implement multimedia information transmission over thepublic service telephone network have not yet been successful, in partby the limited bandwidth of telephone cable and the unavailability ofadequate technology to support copper based multimedia informationtransmission. Broad bandwidth transport is necessitated not only by theneed to carry good quality video information from an informationprovider to the student, but subscriber control signals and ordinarytelephone service as well.

Although optical fiber is capable of providing sufficient bandwidth,even optimistic projections of installation of fiber in the local loopexpect only modest market penetration by the turn of the century andubiquity many years after that. This invention implements the publicswitch telephone network (PSTN) to carry out transport of multimediainformation from one source or multiple sources to a subscriber over asingle loop in the form of copper wire or other medium, including fiber,to help remove distance as a barrier to information transfer ataffordable cost.

DISCLOSURE OF THE INVENTION

According to one aspect of the invention, a public switched telephonenetwork for providing information from a multimedia information serverto any one of a plurality of subscriber premises comprises a telephonecompany central office receiving multimedia information signals from amultimedia information server and orders from a prescribed subscriber.The central office includes a gateway system for providing routing datain response to subscriber orders and a switch for routing multimediasignals from the server to the prescribed subscriber in accordance withthe routing data. An interface at the central office includes a firstmultiplexer/demultiplexer for transmitting or receiving audio telephoneservice signals, subscriber control signals and digital multimediainformation signals on first, second and third signal channels. Eachsubscriber premises includes an interface having a secondmultiplexer/demultiplexer for transmitting or receiving audio telephoneservice signals, subscriber control signals and digital multimediainformation signals on the three signal channels. The interface mayincorporate frequency multiplexing/demultiplexing so that the threechannels are displaced from each other in frequency. A plurality ofsubscriber local loops interconnect each subscriber interface and thecentral office interface. Preferably, the central office interfacecomprises a plurality of interfaces, one for each subscriber.

In accordance with the preferred embodiment, the first channel is abidirectional channel carrying audio telephone service signals betweenthe subscriber and central office. The second channel is a bidirectionalchannel carrying subscriber control signals to the central office andpossibly response signals from the central office, and the third channelis a unidirectional channel carrying digital multimedia informationsignals from the central office to the subscriber. The local loopspreferably comprise copper pair wiring, although optical fiber isanother possibility.

Furthermore, the subscriber interface may include a decoder forconverting an incoming digital multimedia information signal to ananalog signal having a video component. The decoder decompresses theincoming multimedia signal and produces analog video and associatedaudio output signals. Alternatively the multimedia information mayincorporate uncompressed digital signals applied directly to a digitalterminal, such as a personal computer.

In accordance with a particular aspect of the invention, the centraloffice further includes a packet data network responsive to the gatewaysystem for supplying command signals to the multimedia informationserver. Digital multimedia information storage, remote from thesubscriber premises, buffers multimedia information and supplies thesame to the central office interface.

In the preferred embodiment of the invention, the multimedia informationserver comprises a subscriber request processing means, responsive tosubscriber request data, for supplying information request data and asession control means, responsive to the information request data, forsupplying information retrieval data and output control data. Alsoincluded in the server are a data storage means, preferably comprisingplural types of storage media, responsive to the information retrievaldata for supplying program data and an output control means, responsiveto the output control data, for supplying the multimedia information.

Another aspect of the invention involves interaction between subscribersand sources of multimedia information. In accordance with the preferredembodiment, the multimedia server system comprises a number of databases that are transparently shared by a subscriber. When the subscriberqueries a principal data base containing multimedia information and doesnot find the information sought, other data bases sharing resourceseither through the gateway system or outside the gateway, are searched.

A further aspect involves multiple subscriber interaction with themultimedia servers. Groupware functionality incorporated in subscriberresident software enables subscribers to share a session and therebymutually contribute to a multimedia joint presentation.

Various objects and advantages of the present invention will becomereadily apparent to those skilled in this art from the followingdetailed description, wherein only the preferred embodiment of theinvention is shown and described, simply by way of illustration of thebest mode contemplated of carrying out the invention. As will berealized, the invention is capable of other and different embodiments,and its several details are capable of modifications in various obviousrespects, all without departing from the invention. Accordingly, thedrawing and description are to be regarded as illustrative in nature,and not as restrictive.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a system diagram of a PSTN incorporating flow of multimediainformation from a source to a subscriber, in accordance with theinvention.

FIG. 2 is a simplified block diagram of a media server, according to theinvention.

FIG. 3 is a more detailed block diagram of the media server of FIG. 2.

FIG. 4 is a block diagram of multimedia information storage facilitiesof the media server.

FIG. 5 is a functional diagram of a subscriber interface unit.

FIG. 6 is a spectrum diagram showing channelization of a local loop bythe interface unit.

FIG. 7 shows a typical in-the-home configuration providing videotransported over a 1.544 MBPS channel overlaid, with standard telephoneservice signaling.

FIG. 8 is a block diagram of the interface unit in the form of anasymmetrical digital subscriber line (ADSL) system providing simplexhigh-bit-rate access and POTS on a common copper loop.

FIG. 9 is a diagram depicting interaction among server, data base andsubscriber software modules, in accordance with the invention.

FIG. 10 shows the fundamental architecture of software for performingcommunications between the central office and subscribers sharing in amultimedia session.

BEST MODE FOR CARRYING OUT THE INVENTION

Overview

The digital multimedia information service platform shown in FIG. 1 isof an architecture similar to the type described in copendingapplication Ser. No. 07/766,535, filed on Sept. 27, 1991 and entitledPSTN ARCHITECTURE FOR VIDEO-ON-DEMAND SERVICES, incorporated byreference, modified herein to accommodate delivery of multimediaservices to subscribers that include home and institutional (e.g.,school) subscribers at terminals 100 and 120, respectively. Thearchitecture for multimedia delivery, in accordance with the invention,includes four main components: at least one multimedia server 162, agateway system 32, a central office (CO) 10 based transmission systemand the-subscriber terminals. The multimedia server 162 storescompressed multimedia presentations in the form of data files receivedfrom providers of multimedia information (not shown) that may resideoutside the CO 10. Encoded multimedia data is stored on the multimediaserver 162, in for example, digital magnetic tape or digital cassetteformat, at the CO 10. The server 162 may alternatively be external tothe CO 10. The data may be electronically buffered for transmission overa POTS line to the subscriber.

The gateway system 32 performs two main functions. It controls access tothe multimedia server 162 and originates the control messages to set upa high speed link between the servers and subscriber terminals via thetransmission system. The multimedia file server system 162 handlesrequests received from the gateway system 32 through a packet datanetwork 40 and provides a multimedia file feed to the subscriber via thenetwork link. The server is a file management system responsible forinputting multimedia files from providers, storing these files orpassing the real-time data through to the subscriber, keeping track ofsessions, handling all interactive control requests from the subscriber,and controlling all outputs.

The transmission system uses a transmission medium of optical fiber orof telephone cable carrying separate channels of audio telephoneservice, single direction subscriber control signals and multimediasignals, multiplexed/demultiplexed at central office and subscriberinterfaces. Alternatively, a public switched telephone network coupledwith a Public Data Network (PDN) or an Integrated Services DigitalNetwork (ISDN) may be used. Data can be packetized in the PDN andtransmitted to the gateway system 32. When ISDN is used, the data arepacketized in the subscriber terminal itself, which preferably is in theform of a-personal computer. The data alternatively may be synchronizeddata.

Utilizing a communications application program in the terminal, thesubscriber sets up a connection to the gateway system 32. The gateway 32validates the subscriber through a log-in sequence and presents a menuof available multimedia presentations or other forms of data from whichthe subscriber can choose. When a choice has been made, the gatewaysystem 32 provides the multimedia server 162 with the selectioninformation and the network address of the subscriber. The serverassigns a spare port over which it will transmit the information andpasses identification of this port back to the gateway. The gateway 32combines the port identification with the customer identification, andpasses both pieces of information via network 40 to a digital crossconnect (DCC) management system 26, which controls cross connect switch(DCS) system 24 to set up a temporary connection between the relevantinput and output ports. When the connection has been established, thesubscriber may interact with the multimedia application by sendingcommands to the multimedia server 162 and receiving responses at thesubscriber's terminal or work station. The server 162 may, if necessary,access information from another multimedia server to satisfy aparticular request for information.

The multimedia presentation can be full motion video, text, graphics,animation, audio information, etc. Alternatively, the completemultimedia presentation may be transferred to the subscriber terminalwhere it will be stored locally in a high capacity storage device. Allinteractions between the subscriber and the multimedia presentation willthen occur locally at the subscriber terminal. Through use of resourcesharing programming, subscribers can share a session, jointly accessingthe server and authoring a multimedia presentation, a capabilityparticularly useful to students.

The platform adopts existing components of the Public Switched TelephoneNetwork (PSTN) and implements compression techniques to store multimediainformation for subsequent forwarding over interoffice facilities. Theswitching facilities are located in central offices serving residentialsubscribers. Loop electronic devices modify the transmissioncharacteristics of the local copper loop to provide required enhancementto the PSTN and permit delivery of full multimedia information.

High data rate types of multimedia data are encoded to conserve systemresources. For example, analog information is first converted to adigital format and then compressed using, for example, encodingalgorithms standardized by the International Standards Organization(ISOs) Motion Picture Experts Group (MPEG). Another example is the JPEGstandard for images. Each title comprises information stored by a mediaserver as an addressable data file in conventional data processingdevices functioning as a video library. Establishing and monitoringconnections which link a library port transmitting selected informationwith the end subscriber ports that receive the information are performedby a supervisory controller such as a network control system, e.g.,FLEXCOM (TM) software, used to control an electronic digitalcross-connect switch system 24 in the PSTN. The DCS 24, also used forswitching two-way DS-1 rate transmissions, is adapted to additionallyprovide bridging or broadcast of multimedia information to severalsubscribers.

Subscriber local loops having ends equipped with asymmetric digitalsubscriber line (ADSL) devices 18, 124 are connected to the DCS 24. Themultimedia distribution system provides for the simultaneous transportof a one-way 1.544 megabit per second (MBPS) signal over the sametwisted pair transmitting voice messages to the residential subscriber.The ADSL transported signal is demultiplexed and the 1.544 Mbit portionis then decoded using appropriate standard techniques to deliver amultimedia information signal.

It can be anticipated that fiberoptic technology will replace existingcoaxial and twisted pair connectivity with corresponding enhancementsmade to switching and routing equipment in the PSTN. Hence, withreference to FIG. 1, assume the subscriber is a school or other sitehaving multiple student terminals, as at institutional site 100.Connectivity from the multimedia server on optical fiber may bemultiplexed to student terminals on separate DS1 channels (not shown).Each student will communicate with the server through a personalcomputer to develop a multimedia presentation. As will be describedlater, in accordance with an aspect of the invention students areenabled to share a common session with the server, or with multipleservers.

PSTN Architecture

Referring now to FIG. 1 in more detail, PSTN central office (CO)equipment 10 provides connectivity from information providers (notshown) to media server system 162 and subscribers 100 and 120. CO 10,which may but not necessary is telephone company central officeequipment, includes a conventional voice switch that includesconventional elements to detect off-hook, service requests, callcompletion (i.e., ring trip), a DTMF decoder and dial pulse detector.The voice switch also includes a telephone call connection switch forrouting voice circuits among the various ports. These elements are allconventional.

An institutional or residential subscriber at premises 100, 120 isconnected to the CO 10 through an interface consisting of anasymmetrical digit subscriber line (ADSL) system. The ADSL systemcomprises a pair of ADSL devices 124 and 18 on the subscriber and COends of the subscriber loop 20 for multiplexing (i) voice and signalinginformation from the CO voice switch and (ii) digital multimedia datafrom DCS 24.

In addition to providing multimedia programming, the server system 162accepts multimedia programming from multimedia information providers forlater transmission.

ADSL system 18, 124 multiplexes data on subscriber loop 20 usingfrequency domain multiplexing, dividing the available loop bandwidthinto multiple segments or channels. However, other types ofmultiplexing, such as time domain (TDM), are possible. Base band audioand signaling below 4 kilohertz (kHz) provides connectivity for aconventional telephone services available on the "plain old telephonesystem" (POTS). Alternatively, ISDN channel requirements consume thebottom 80 kHz of loop bandwidth. Reverse channel digital packetinformation is positioned between 80 and 90 kHz providing approximately16 kilobits per second (kbps) connectivity from the subscriber premisesto a packet switched network such as ISDN network 12 over a D-channelinterface. Compressed multimedia data is contained between 100 and 400kHz to provide a 1.6 MBPS channel for transporting the multimedia dataover subscriber loop 20 to premises 100/120.

ADSL 18 carries out error correction and, as shown in FIG. 6, dividesthe available loop bandwidth into three channels 302, 304 and 306. Baseband audio and signaling below 4 kilohertz (kHz) provide connectivityfor a conventional telephone services available on the "plain oldtelephone system" (POTS). Alternatively, ISDN channel requirementsconsume the bottom 80 kHz of loop bandwidth. Reverse channel digitalpacket information, centered on 95 kHz., provides 8 kilobits per second(kbps) of handshaking protocol between the subscriber- and CO-side ADSLs124 and 18 to test the copper pair transmission path, and approximately16 kbps connectivity from the subscriber premisses to a packet switchednetwork, such as the ISDN network over a D-channel interface. The 16kbps signal is stripped by the ADSL 18 and sent to the CO 10. Compresseddigital video information is contained within the frequency range ofabout 100 and 500 kHz to provide about a 1.6 mbps (1.544 mbps) channelfor transporting video/audio data over loop 20 to subscriber premises120.

The frequency channel represented by segment 302 in FIG. 6 thusestablishes a 2-way channel used to provide standard POTS service orISDN (2B+D) service over the subscriber loop 20. Channel 304 is anup-stream only (subscriber to CO), low speed data channel. 8 kbps ofthis channel are used for transfer of operations, administration,maintenance, and provisioning (OAM&P) data for the ADSL unit.Optionally, the channel may provide response messages or the like fromthe CO, and hence, may be considered a bidirectional channel. Theremaining 16 kbps, compatible with X.25 or D channel interfaces ofBRI-ISDN, is used to interface with a packet switch allowing thesubscriber to interact with the network and/or the 1.544 mbps signalprovider.

Channel 306 carries a down-stream only (CO to subscriber) digital signalproviding 1.544 mbps transport (1.6 mbps with overhead) for carrying thedigitized compressed video signal. The lower edge of channel 306 is setat 120 kHz., chosen to minimize channel loss and allow appropriatebandwidth for base band channel 302 and reverse channel 304 and tominimize interference from impulse noise. The combined digitaldown-stream signal utilizes the DS1 bit map specified byANSIT1.403-1989.

Because data channels 304 and 306 are unidirectional (although channel304 optionally may be operated bidirectionally, as mentioned above), thesystem does not experience self-NEXT (near end cross-talk). This allowsconcentration on the interface and interference from impulse noisebecause the ADSL system is loss-limited rather than NEXT limited.Impulse noise exposure can be reduced by using a pass band technique asopposed to a base band approach since impulse noise affects are greatestbelow 40 kHz. Therefore, a modulation technique such as QuadratureAmplitude Modulation (QAM) is preferred over a 2B1Q base band system.

ADSL multiplexer 200 shown functionally in FIG. 5, within each ADSL unit18, 124, supports transmission of a one-way 1.544 mbps digital signalalong with a POTS or a BRI-ISDN signal over a single non-loaded copperpair. This configuration provides service to a customer over copper looplengths of up to 18,000 feet, conforming with Carrier Serving Area (CSA)and resistance design rules. Discreet multi-tone is an alternative.

The ADSL system (the hardware block diagram is shown in more detail inFIG. 8) provides simplex high-bit-rate video data and POTS connectivityto a subscriber over a common copper loop with transport capability todeliver a one-way high-bit-rate data stream with POTS or ISDN basicaccess multiplexed at baseband. Each ADSL on the subscriber- and CO-sides includes an error correction circuit 21 implementing an errorcorrection algorithm, such as the Reed-Sullivan algorithm, forcorrecting errors that arise as a result of transmission of data on atwisted pair of copper lines. The subscriber- and CO-side ADSLs onopposite ends of the twisted copper pair carry out "handshaking" whileimplementing the algorithm to reduce error in the video signal to aminimum.

The multiplexer 200 residing in each subscriber-side ADSL includes, inaddition to a frequency converter for channelizing the incoming signalinto 1.544 Mbps, 16 Kbs and 8 Kbps components, a splitter/filter (notshown) for separating the standard POTS signal from the multimediacomposite. Hence, the multimedia component incoming on the twistedcopper pair is transparent to a standard phone resident on the line atthe usual network interface device (NID).

Subscriber and CO ADSL interface units 124 and 18 are synchronized toensure that both subscriber and CO side units derive timing from onemaster clock to prevent data loss. Preferably, the units derive timingfrom the incoming 1.544 mbps signal. Subscriber end ADSL equipment ispowered locally from the customer premises; CO end ADSL equipment ispreferably powered by an external source of DC input voltage in therange of between -42.5 and -55 VDC.

FIG. 7 shows a typical in-the-home configuration which providesmultimedia information transported over the 1.544 mbps channel. Theunidirectional 1.544 mbps signal carried by the ADSL system has either aSuperframe Format (SF) or an Extended Superframe format (ESF). TheSuperframe format consists of 24 consecutive 8-bit words preceded by onebit, called the framing bit (F-bit), for a total of 193 bits per frame.The F-bit is time-shared to synchronize the ADSL interface equipment andto identify signaling framing. Twelve consecutive frames form aSuperframe. A line code used with a Superframe format is bi-polarreturn-to-zero, also known as Alternate Mark Inversion (AMI).

The ESF format consists of 24 consecutive frames, each of which includes192 information bits preceded by 1F-bit for a total of 193 bits perframe. The F-bit is used for basic frame synchronization, a cyclicredundancy check and a data link. Twenty-four frames form a Superframe.The line code used with the ESF is either AMI, bi-polar 8-zerosubstitution (B8ZS), or AMI with Zero-Byte Time Slot Interchange(ZBTSI).

Media Server System The media server system 162, shown in further detailin FIGS. 2-4. processes all requests from gateway system 32 forproviding multimedia and video file feeds to customer premises via theDCS and ADSL systems. The media server system performs input of videoand other information files from multimedia information providers,stores these files, monitors and records subscriber sessions, processesall interactive control requests from subscribers, and controls alloutputs to the subscribers.

The media server system 162 also processes and supplies multimediaservices including interactive learning, interactive games, and otherpresentations. The server stores and processes all data required for themultimedia applications including text, still pictures, audio, andpartial and full motion video, as well as interactive applicationscripts.

Media server system 162 includes eight major components shown in FIG. 2:input device 210, Q.931 interface 230, librarian 250, storage manager270, session manager 320, output controller 310, interactive processor350 and multimedia application processor 370. Input device 210 includesa plurality of DS-3 Input ports 212 or other input devices for receivingmultimedia data including encoded digital video signals. Alternatively,the data may be supplied from a magnetic tape or the like source ofstored data. Multimedia information in MPEG or other standard of encodedformat is supplied to output controller 310 or to gateway interface 410(FIG. 3) to be routed to session manager 320 for eventual storage by theserver system.

The network control software of the media server in combination withmanagement resources of the PSTN controls the "network session" betweenan output controller 310 of the media server and subscriber ports. Thesession manager 320 also maintains a record of relevant data regardingeach session which is forwarded to a customer billing system.

Q.931 interface 230 provides connectivity between interactive processor350 and ISDN Interface 12 (FIG. 1). Interactive processor 350 includes auser control monitor 352 and a control channel filter 354. Interactiveprocessor 350 receives command data over the ISDN from subscribersrunning interactive programming from the media server. Interactiveprograms include multimedia presentations. The interactive processor 350also receives command data from the subscriber for interactive controlof multimedia applications and data objects. These commands are passedto session manager 320 for further processing and control of multimediaprogramming.

Data to be stored in or retrieved from memory is first routed throughlibrarian 250 and, under its control, storage manager 270 either storesthe program data or retrieves and provides previously stored programdata to output processor 330.

Media librarian 250 controls distribution of video, audio, still imagedata and text selections to session manager 290 in response toinformation requests from the session manager and multimedia applicationprocessor 370 that includes an application script and a multi-media toolkit. Referring to FIG. 3, the librarian further monitors and record infeature index 252 the storage location of all video selections formultimedia applications. The librarian also records a history of accessto multimedia information provided during each prescribed, e.g.,twenty-four hour period in usage data accumulation system 260. The usagedata is supplied to usage probability processor 262 to establish anintelligent cache using DRAM storage 278 for rapid access and highlyaddressable storage of features.

Feature indexes 252 maintain a catalog of data and support processingfor storing all locally stored multimedia information. This includes theallocation of storage media type and space, maintenance of addressingtables for program stat and frame indices, and indexes for all volumes.The program listing data is supplied to a menuing system supported bygateway 32 (FIG. 1) via packet data network 40.

Feature indexes system 252 performs required catalog maintenancefunctions including input of new multimedia information into the system.The catalog maintenance system determines the priority of the incomingmultimedia data and allocates appropriate storage to the data. Once thefile space is allocated and the file is stored, the volume indexes areupdated, the frame positions of the program are calculated and frameaddressing tables are created and stored. The frame addressing tablesare used to address multimedia information or a data object from anyposition in the multimedia production.

When it is determined that stored multimedia production is no longerrequired, media librarian 250 removes the program data from the filecatalog. The record to be deleted is then flagged by the systemadministrator.

The catalog system updates multimedia data as the multimedia productionsare loaded into the media server. The updated catalog information issupplied by librarian 250 of the media server to gateway 32.

Storage channel management processor 274 controls the flow of databetween all storage devices and output control processor 330. Inputcontrol processor 210 receives multimedia data from the multimediainformation providers. Multimedia data input is accepted asappropriately encoded multimedia information. All data is stored forplay at a subscriber's request.

Session manger 320 includes a session trace 314, a VIP supervisor, anetwork optimizer and a session supervisor 312. The session supervisor312 which manages all program sessions including system access bymultimedia subscribers and input and output to, from and through themedia server by multimedia information providers. Session supervisor 312tracks and records all data considered pertinent to a subscriber'ssession including output port, multimedia data being played ormultimedia application address, feature index data, feature frame data,and session condition.

Session supervisor 312 maintains a matrix of routing information foreach session, including what subscribers are assigned to a given outputport, and the source of the input data, that is, the input port of localstorage. A file play clock uses the total number of frames in a givenfeature to estimate, by time, the frame position for that feature. Thisdata is provided to the session registers for tracking frames for eachlogical subscriber session and is used to restart an interruptedsession. Session supervisor 312 discontinues register updates upondetection of a session interruption.

The session supervisor also receives all requests from gateway 30 viaQ.931 interface 230 and control channel filter 354 to establish asession and for file retrieval.

Interactive processor 350 processes incoming commands from subscribersites once a session is established by the gateway. These commandsinclude requests by multimedia work stations. The incoming data isinterrogated for content and selectively forwarded to the appropriatemodule for processing, that is, the multimedia application processor formultimedia applications.

Control channel monitor 352 monitors each subscriber's control channelto detect a communication failure. In the event of a failure, sessionmanager 320 is informed and corrective action is initiated.

Communications Software

FIG. 9 shows the software architecture for setting up communicationsbetween the subscriber terminals and the gateway, in accordance with thepreferred embodiment. There are two principal programming modules: aserver resident module 500 and a subscriber module 502 resident atcustomer premises equipment, interconnected with each other through DS-1and/or ISDN channels. Within the server resident program module 500 is aresident database for storing multimedia information derived from themedia server, an interface to the gateway system 32 and control softwarefor controlling playback of session information at the terminal. Anadditional general utility communication program enables dialogue to becarried out between the subscriber and server, or between subscriberscooperating in a session.

The CPE resident software contains counterpart database, control(playback) and gateway interface software. The CPE control software willrespond to subscriber commands, such as the commands generated by theposition of a mouse, to send a command signal to the server. The server,in turn, will interpret the command signal and transmit appropriatemultimedia information on the DS-1 channel to the subscriber. In thisregard, the server reads the command signal, customizes or interprets itin view of the session being conducted, and makes a decision as to whatnext piece of multimedia information should be presented. The residentsoftware loads the segments of information to be sent to the subscriberinto a buffer, notifies the subscriber software that the next screen isready to be downloaded, and the multimedia information sent. The purposeof the buffer is to enable construction of a seamless multimedia sessioncomposed of multiple data files that are assembled in sequence.

Through interactive communication with the server, the subscriber isable to redirect the multimedia session at each logical branch. Thesubscriber supplies the various control signals to create a multimediaperformance to the authoring software module that recreates a new copyof a series of old multimedia information elements. The resulting copyis saved at the server and may be accessible to other subscribers, withcertain constraints, under control of a system administrator.

Alternatively, a multimedia presentation may be comprised of multiplemultimedia elements that are stored in a number of buffers within theserver and indexed by a script stored at the subscriber terminalplayback module for each presentation. The buffer size at the servermemory is dependent on the amount of time required to access the database and retrieve the elements, and to process the elements for deliveryto the subscriber. Decision alternatives available to the subscriberduring an interactive session are sent by the server to the playbackunit of the subscriber. The playback module in the resident softwarethus includes the script itself and portions of the script. For eachdecision point, queuing information is provided to the server so thatthe server can ready other presentations while the selection of the nextpresentation is still carried out at the subscriber terminal. Forexample, four selections may be queued to the subscriber, and theplayback module is controlling a particular one to play out.

If the media server is found not to contain a particular piece ofinformation sought by the subscriber, the gateway system 32 is notifiedby the server, and other databases may be automatically searched for therequired information. These databases may be resident at different mediaservers.

Alternatively, the subscriber may be notified of the failure of themedia server database to satisfy the current information request and thesubscriber given an option to search other data bases within a singlemedia server, at another server of the media server system or outsidethe server system. As another alternative, other databases, broadbandchanneled to the media server outside the gateway system, may besearched. Intercommunication between data bases may be performed on aswitched DS-3 line implementing a broadband gateway system, as shown inFIG. 9, or within an synchronous transfer mode (ATM) environment.

Although a multimedia authoring session ordinarily will involve onesubscriber at a time, it is possible to enable multiple subscriberterminals to share a session using known "groupware" software at thesubscriber terminals, as shown in FIG. 10, or communication softwaresuch as Rainbow(TM) or PC Anywhere(TM). Alternatively, the subscribersmay coauthor a multimedia presentation using two B-channels of ISDN, aseparate ISDN line using a second ISDN communication board or E-mailcommunication between subscribers operating a common session. Thisenables students to jointly author a multimedia presentation, and otherforms of teaming efforts to be carried out.

As still another possibility, video communications may be establishedbetween server and subscriber terminals or between subscribers. Forexample, subject to federal regulations, a video camera may be providedat one subscriber terminal at a classroom, and video signals sent to asecond terminal where an instructor resides to enable an instructor toview students during an interactive session.

The server resident software monitors the amount of time a subscriber ison line, and together with the gateway system, performs billingoperations. If the subscriber remains on line for more than a prescribedamount of time without sending any command signals to the server, theserver automatically drops the line, and is free to service othersubscribers. However, when the subscriber next sends a command signal,the link between the server and subscriber is automaticallyreestablished.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationan example and is not to be taken by way of limitation, the spirit andscope of the present invention being limited only by terms of theappended claims. As one example, although the network, as described,implements an ISDN interface 12, as shown in FIG. 1, an X.25 interfaceis an alternative. As another, although all three channels, POTS,command and video are preferably multiplexed or a common transmissionmedium, as described, it is also possible within the scope of thisinvention, to transmit and/or receive at lease one of the channels on aseparate medium, such as a cellular link.

What is claimed is:
 1. A multimedia information server for providingcompressed digital multimedia information over a public switchedtelephone network comprising:an input device for receiving multimediadata; a multimedia storage system for storing multimedia information andsupplying said multimedia information in response to informationretrieval data; a storage manager for managing said multimediainformation stored in said multimedia storage system; a multimediaapplication processor for processing said multimedia information storedin said multimedia storage system; a librarian for controlling saidstorage manager, said input device and said multimedia applicationprocessor; a session manager, responsive to information request data,for supplying information retrieval data and output control data and forcontrolling communication sessions; an output controller, responsive tooutput control data, for supplying multimedia information; an interfacehaving an external connection, responsive to subscriber request data,for supplying information request data; and an interactive processor,connected to said session manager, said multimedia application processorand said interface, for causing multimedia information to be processedin accordance with control signals received via said interface; whereinsaid librarian comprises feature indexes and a frame index, a usage dataaccumulation circuit, a usage probability processor, a real time MPEGencoder, and a multi-pass MPEG encoder.
 2. A multimedia informationserver as recited in claim 1, wherein said multimedia storage systemcomprises plural types of storage media and supplies program data.
 3. Amultimedia information server as recited in claim 1, wherein said serversupplies digital multimedia information from a plurality of databasesthat are transparently shared by a subscriber and includes a queryprocessor which, when said subscriber queries a principal database ofsaid plurality of databases containing multimedia information and doesnot find the information sought, searches secondary databases of saidplurality of databases.
 4. A multimedia information server as recited inclaim 1, wherein said interactive processor is responsive to signalsfrom groupware incorporated within subscriber resident software whichenables multiple subscriber interaction and enables subscribers to sharea session and thereby mutually contribute to a multimedia jointpresentation.
 5. A multimedia information server as recited in claim 1,wherein said interactive processor comprises a user control channelmonitor and a control channel filter.
 6. A multimedia information serveras recited in claim 1, wherein said multimedia application processorcomprises an application script and a multimedia tool kit.
 7. Amultimedia information server as recited in claim 1, wherein saidstorage manager comprises, a storage channel management circuit and aplurality of memory controllers, respectively corresponding to aplurality of types of storage media.
 8. A multimedia information serveras recited in claim 1, wherein said multimedia information serverestablishes communications with an interface in a subscriber terminal toinitiate an interactive multimedia session for transmitting andreceiving compressed multimedia information therebetween and interpretscommand signals transmitted from said interface, in view of theinteractive multimedia session being conducted, in order to createinformation request data and to transmit digital multimedia informationcorresponding to said information request data to said subscriberterminal.
 9. A multimedia information server as recited in claim 3,wherein said query processor searches secondary databases of saidplurality of databases through a gateway system.
 10. A multimediainformation server as recited in claim 7, wherein said plurality oftypes of storage media comprise archival tapes, high speed tape storageunits, disk storage units, and DRAM storage and wherein said pluralityof memory controllers comprises an archival tape controller, a highspeed tape controller, a disk controller, and a DRAM storage controller.11. A multimedia information server as recited in claim 8, wherein oneof said command signals comprises a command signal which instructs themultimedia information server to create and save a multimedia program,constructed in accordance with command signals previously transmitted inthe interactive multimedia session, for access by other subscribersunder control of a network administrator.
 12. A multimedia informationserver as recited in claim 11, wherein said multimedia informationserver provides information to the subscriber for the transmission ofsaid command signals.
 13. A multimedia information server as recited inclaim 8, wherein said command signals respectively identify indexescorresponding to digital multimedia information stored in a multimediadatabase of the multimedia information server.
 14. A multimediainformation server according to claim 13, wherein said multimediainformation server provides information to the subscriber for thetransmission of said command signals respectively identifying saidindexes.